Simple joint gazebo simulation
Table of Content
launch gazebo and spawn our simple_joint robot
- apply torque to link from gazebo gui
- Add gazebo_force plugin
- apply torque from command line
launch gazebo#
urdf#
```xml title=”robot_v1.urdf|
<material name="blue">
<color rgba="0 0 0.8 1"/>
</material>
<material name="black">
<color rgba="0 0 0 1"/>
</material>
<joint name="word2base" type="fixed">
<parent link="world"/>
<child link="base_link"/>
<origin xyz="0.0 0.0 0.12" rpy="0.0 0.0 0.0"/>
</joint>
<link name="base_link">
<inertial>
<mass value="10" />
<inertia ixx="0.4" ixy="0.0" ixz="0.0" iyy="0.4" iyz="0.0" izz="0.2"/>
</inertial>
<collision>
<geometry>
<cylinder radius="0.05" length="0.24" />
</geometry>
</collision>
<visual>
<geometry>
<cylinder radius="0.05" length="0.24" />
</geometry>
<material name="black"/>
</visual>
</link>
<link name="second_link">
<inertial>
<mass value="0.18" />
<inertia ixx="0.0002835" ixy="0.0" ixz="0.0" iyy="0.0002835" iyz="0.0" izz="0.000324" />
</inertial>
<origin rpy="0.0 0.0 0.0" xyz="0.0 0.0 0.0" />
<collision>
<geometry>
<box size="0.05 0.05 0.15" />
</geometry>
</collision>
<visual>
<geometry>
<box size="0.05 0.05 0.15" />
</geometry>
<material name="blue"/>
</visual>
</link>
<joint name="base_to_second_joint" type="continuous">
<parent link="base_link"/>
<child link="second_link"/>
<axis xyz="0 0 1"/>
<origin xyz="0.0 0.0 0.2" rpy="0.0 0.0 0.0"/>
</joint>
<gazebo>
<plugin name="gazebo_ros_joint_state_publisher" filename="libgazebo_ros_joint_state_publisher.so">
<update_rate>50</update_rate>
<joint_name>base_to_second_joint</joint_name>
</plugin>
</gazebo>
<gazebo reference="base_link">
<material>Gazebo/Black</material>
</gazebo>
<gazebo reference="second_link">
<material>Gazebo/Red</material>
</gazebo>
```
launch#
python title="gz_sim.launch.py"
from launch import LaunchDescription
import os
from launch_ros.actions import Node
from ament_index_python.packages import get_package_share_directory
from launch.actions import AppendEnvironmentVariable, DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
import xacro
PACKAGE = "simple_joint"
WORLD = "empty.world"
URDF = "robot_v1.urdf"
def generate_launch_description():
ld = LaunchDescription()
pkg = get_package_share_directory(PACKAGE)
gazebo_pkg = get_package_share_directory('gazebo_ros')
verbose = LaunchConfiguration("verbose")
arg_gazebo_verbose = DeclareLaunchArgument("verbose", default_value="true")
world = LaunchConfiguration("world")
arg_gazebo_world = DeclareLaunchArgument("world", default_value=WORLD)
resources = [os.path.join(pkg, "worlds")]
resource_env = AppendEnvironmentVariable(
name="GAZEBO_RESOURCE_PATH", value=":".join(resources)
)
sim_time = LaunchConfiguration("sim_time")
arg_sim_time = DeclareLaunchArgument("sim_time", default_value="true")
robot_description_path = os.path.join(pkg, "urdf", URDF)
doc = xacro.parse(open(robot_description_path))
xacro.process_doc(doc)
robot_description = doc.toxml()
robot_state_publisher = Node(
package="robot_state_publisher",
executable="robot_state_publisher",
parameters=[{"use_sim_time": sim_time, "robot_description": robot_description}],
)
gazebo = IncludeLaunchDescription(
PythonLaunchDescriptionSource([os.path.join(
gazebo_pkg, 'launch', 'gazebo.launch.py')]),
launch_arguments={'verbose': verbose, "world": world}.items()
)
spawn_entity = Node(
package="gazebo_ros",
executable="spawn_entity.py",
arguments=["-entity", "demo", "-topic", "robot_description", "-z", "0.0"],
output="screen",
)
ld.add_action(resource_env)
ld.add_action(arg_gazebo_verbose)
ld.add_action(arg_gazebo_world)
ld.add_action(arg_sim_time)
ld.add_action(robot_state_publisher)
ld.add_action(gazebo)
ld.add_action(spawn_entity)
return ld
Apply torque#
- Apply torque to joint
gazebo joint state plugin
<gazebo>
<plugin name="gazebo_ros_joint_state_publisher" filename="libgazebo_ros_joint_state_publisher.so">
<update_rate>50</update_rate>
<joint_name>base_to_second_joint</joint_name>
</plugin>
</gazebo>
Apply Force/ Torque using Wrench msg#
Create topic with Wrench message
Note
xml
<joint name="base_to_second_joint" type="continuous">
<parent link="base_link"/>
<child link="second_link"/>
<axis xyz="0 0 1"/>
<origin xyz="0.0 0.0 0.2" rpy="0.0 0.0 0.0"/>
<dynamics damping="0.1" friction="1"/>
</joint>
xml
<gazebo>
<plugin name="gazebo_ros_force" filename="libgazebo_ros_force.so">
<link_name>second_link</link_name>
<force_frame>world</force_frame>
</plugin>
</gazebo>
### Wrench msg